Large quantities of oil are presently transported from oil-producing nations to oil-consuming nations by various means, including large sea-going vessels. As the number and size of such vessels increases, the probability of a large oil spill occurring, with its attendant, serious environmental consequences also increases. A number of such accidents have occurred which have resulted in contamination of beaches with possibly permanent environmental damage.
Substantial progress has been made in the recovery of oil spilled on large bodies of water. Typically, the oil spill is surrounded by a floating boom to contain the spill. Conventional vacuuming and filtering equipment are then employed to remove the oil from the circumscribed area, as the oil will continue to float on the surface of the water as long as the more volatile components of the oil have not evaporated. Such efforts have proven effective as long as the oil remains at sea, the booms are quickly deployed, and the sea is not too rough.
Recovering oil from beaches is substantially more difficult than recovering oil from the sea. The beach environment contains a large number of organisms which live on the beach, and below the surface of the beach up to a depth of approximately one foot. In contrast, the upper layer of the ocean is a relatively "dead" ecological environment. Therefore, oil spills which have washed up on beaches generally cause significantly greater ecological damage than oil spills which are contained at sea.
Unfortunately, no currently known technologies have been successful in recovering oil directly from beaches in an ecologically acceptable manner. Presently, the most effective method of cleaning oil contaminated beaches is to wash the spilled oil back into the ocean so that the boom and vacuum method described above can be employed. This technique is only successful if the oil spill is fresh (i.e., the volatiles have not evaporated). If the oil has begun to evaporate, the beach deposit becomes a heavy sludge which can only be washed off with steam or extremely hot water at high pressure. This combination destroys the beach and is injurious to the organisms which live on and under the beach.
Once substantial evaporation of the oil has occurred, the only current techniques which are at all successful in removing the oil involve removing the top layer of sand or gravel from the beach with shovels, treating the same and redepositing the sand/gravel back onto the beach. This process completely destroys the ecological activity in the most ecologically active layer of the beach, and is also an extremely expensive procedure. In addition, this technique is slow, allowing large segments of contaminated beaches to exist for some time. As a result thereof, water fowl, turtles, and other marine animals, etc., which inhabit the beach/ocean interface become contaminated.
Various prior art devices have been described for treating contaminated beaches. The amphibious vehicle disclosed in U.S. Pat. No. 4,769,142, to Withnal, is propelled on the surface of the beach by large rollers which support an oil-absorbent sponge on the perimeter thereof. As the rollers move along the surface of the beach, the sponge absorbs the oil. The oil is removed from the sponge by pinch rollers. The roller sponge described by Withnal would only be effective at removing oil from the surface of the beach if the oil had not begun to evaporate. Furthermore, this device does nothing to treat the first foot or so of material under the beach surface which contains substantial numbers of living organisms.
In another design disclosed in U.S. Pat. No. 4,492,001, to Hedrenious, absorbent material is discharged through a duct onto the beach. The oil is absorbed by the sorbent material for later withdrawal from the surface such as by a vacuum. The Hedrenious device would also only be effective during the early stages of a beach contamination before the oil had begun to evaporate. In addition, this device would also fail to treat any portion of the beach below the immediate top surface thereof.
In addressing the problem of treating the entire vertical depth of the beach which may be contaminated, Wendt et al. disclose a cryogenic beach-cleaning device in U.S. Pat. No. 4,157,016 which freezes the upper layer of the beach with a cryogenic fluid such as liquid nitrogen. A tractor-like device drives a shovel which scoops up and breaks up the frozen beach surface for later reprocessing. This technique would certainly destroy all of the organisms in the treated layer and suffers from the processing costs which are presently encountered by the manual shoveling technique.
In view of the above, a need exists for a device which can effectively remove oil deposited on a beach, whether the oil has begun to evaporate or not, without substantially disturbing the physical structure of the beach or killing the organisms which reside thereunder.